Currently, in a communications system, fiber optic communication is generally performed in an intensity modulation with direct detection (IM-DD) manner. However, chirping in the system and dispersion on a link cause power fading of a modulating signal and affect normal transmission of a signal.
In the prior art, at a sending end, a signal that is input in a bit manner undergoes quadrature amplitude modulation (QAM) mapping, undergoes up-conversion processing, is sequentially input to a drive and an optical modulator, and then enters a fiber channel; and at a receiving end, a signal is received from the fiber channel, sequentially input to an optical amplifier, a filter, and an optical-to-electrical converter, and then output in a bit manner. However, in the prior art, a signal spectrum obtained by the receiving end is continuous, but for a spectrum near a subcarrier (that is, a fading point) where power fading occurs, signal spectrum validity is damaged due to existence of noise, so that valid data cannot be recovered.